With most of the data now in for April sales of plug-in electric cars, it's looking as though the first four months of 2015 aren't seeing notably higher numbers than those of 2014.

As always, there's some slop in the numbers because Tesla Motors, Fiat Chrysler, and Kia Motors refuse to break out their plug-in car sales.

But the data thus far lead to an interesting question: How will it be received if 2015 electric-car sales only match those of 2014?

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Worse yet, what if they come in slightly lower?

We think it's entirely possible that 2015 U.S. sales will only roughly equal 2014 sales.

Many factors remain to be seen over the next eight months, among them the actual launch date of the 2016 Chevrolet Volt plug-in hybrid.

2016 Chevrolet Volt

2016 Chevrolet Volt

Its first-generation predecessor has had one of the longest run-outs of any car we can think of, with sales in the first four months of this year not even breaking 1,000.

The 2016 Volt will have a phased launch, and we'd lay money on the notion that the first sales will take place in California.

But whether those sales are in September or November--and how quickly production, marketing, and sales ramp up--will have a major effect on this year's totals.

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Two game-changing electric cars won't arrive until next year: the 2017 Chevrolet Bolt EV, and the second-generation Nissan Leaf.

Both those cars will have significantly longer ranges than the vehicles they replace--200 miles for the Bolt EV versus the current Spark EV's 82 miles, and some distance between 120 and 200 miles for the Leaf.

Some have suggested that there will be an interim Leaf upgrade for its last production year of 2016, boosting its rated electric range from today's 84 miles into three-digit territory.

Tesla Model X prototype photographed on test, California, Feb 2015. Photo by Simerjit Dhaliwal.

Tesla Model X prototype photographed on test, California, Feb 2015. Photo by Simerjit Dhaliwal.

That too could juice sales this year.

But this year's sales may have slowed precisely because electric-car advocates and fans know that those two new vehicles will arrive in less than 18 months.

The phenomenon, known as "Osborning," is a reduction in sales of an existing product once a new and far better one has been announced for a future date.

MORE: Who Buys Plug-In Electric Cars, And Why? CA Report Explains It All For You

Finally, there's product cadence: The Leaf is now long in the tooth, the 2016 Volt will only have an effect at the end of the year.

The same can be said of the Tesla Model X if it launches on schedule sometime in the second half of 2015.

The Model X, in fact, is the sole high-volume new entry to hit the market this year, whereas last year the BMW i3 surprised everyone by selling 1,000 a month in several months.

2015 Nissan Leaf

2015 Nissan Leaf

As always, Tesla remains the unknown, with analysts and journalists creating all sorts of approximations to estimate the data the factory refuses to release.

The new P85D and 70D Model S versions are probably giving the company a boost, as early Tesla owners trade in their cars and new owners continue to come to the brand, but that company's big news this year will be the Model X.

Every other vehicle expected to launch between now and December will likely be low-volume--selling 50 to 300 a month--which just doesn't move the needle much on a total of more than 100,000 vehicles a year.

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One final factor: Georgia's $5,000 income-tax credit for purchase of an electric car goes away on July 1.

That may well squelch sales of the Nissan Leaf in the greater Atlanta area, which has been one of its sales strongholds over the last year to 18 months.

Regrettably, if this year's plug-in sales are flat, advocates will have to contend with more of the same kind of uninformed commentary that was seen last month when electric and hybrid cars were lumped together by Edmunds in a sales report.

2015 Toyota Prius Liftback

2015 Toyota Prius Liftback

The headline on many articles that covered the Edmunds report referred only to sales of electric cars, despite the fact that hybrids outweighed them in volume by an order of magnitude.

That meant the hybrid fall swamped any news, pro or con, in electric-car sales volumes.

Such articles are emblematic of the lack of understanding of the long-term market for plug-in electric vehicles and the global forces driving the technology.

But with all of that said: We expect 2016 to be an impressive year for plug-in sales, and 2017 to be better yet.


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